Merge "fix tox python3 overrides"

tox.ini

@@ -20,9 +20,11 @@ whitelist_externals = find
 sitepackages = True
 
 [testenv:pep8]
+basepython = python3
 commands = flake8
 
 [testenv:cover]
+basepython = python3
 commands =
   coverage erase
   find . -type f -name "*.pyc" -delete
@@ -30,9 +32,11 @@ commands =
   coverage report
 
 [testenv:venv]
+basepython = python3
 commands = {posargs}
 
 [testenv:docs]
+basepython = python3
 commands = python setup.py build_sphinx
 
 [flake8]
@@ -41,6 +45,7 @@ exclude=.venv,.git,.tox,dist,*lib/python*,*egg,build,doc/source/conf.py,releasen
 
 
 [testenv:bindep]
+basepython = python3
 # Do not install any requirements. We want this to be fast and work even if
 # system dependencies are missing, since it's used to tell you what system
 # dependencies are missing! This also means that bindep must be installed